Method for in-situ preparation of TMDs / TMOs heterojunction based on vulcanized TMOs

Abstract

The invention discloses a method for in-situ preparation of a TMDs / TMOs heterojunction based on vulcanized TMOs, and belongs to the technical field of two-dimensional materials, the TMOs are partially vulcanized by adding a chalcogenide elementary substance to form the TMDs / TMOs heterojunction, and the prepared heterojunction is high in crystallization quality and large in size; the thickness of the heterojunction can be accurately regulated and controlled by changing the dosage of the chalcogenide elementary substance; the single-layer TMDs / TMOs and the multi-layer TMDs / TMOs are prepared, the TMDs / TMOs heterojunction is prepared in one step by adopting a CVD method, the preparation process is simplified, and the production efficiency is improved. And the growth on different types of substrates can be realized. The problems that in a traditional preparation method, operation is complex, and the sample size is small are solved, and a new thought and method are provided for preparation of the two-dimensional material heterojunction.

Description

Technical Field

[0001] The present invention belongs to the technical field of two-dimensional material preparation, and specifically relates to forming a TMDs / TMOs heterojunction by partially sulfiding transition metal oxides (TMOs) by adding chalcogen elements using a chemical vapor deposition (CVD) method. Background Art

[0002] A heterojunction is an interface region formed by the contact of two different materials, which often has excellent photoelectric properties that cannot be achieved by the PN junctions of the two materials. It is suitable for making ultra-high-speed switching devices, solar cells, and semiconductor lasers. For two-dimensional materials, the formation of a heterojunction can further improve the performance of the material, such as carrier mobility and photoelectric conversion efficiency.

[0003] Transition metal chalcogenides (TMDs) and transition metal oxides (TMOs) are considered key materials for realizing future applications of nanotechnology due to their unique electronic, physical, chemical and mechanical properties. TMDs are typical two-dimensional materials with adjustable band gap and number of layers, high thermoelectric conversion effect and high carrier mobility. The application of two-dimensional TMDs depends largely on the construction of van der Waals (vdWs) heterostructures, in which the constituent materials of the heterostructures can not only maintain their own properties but also produce new physical and chemical properties at the interface. Studying the properties of heterostructures, including interlayer interactions, is very important for understanding their intrinsic physics. TMOs are of various types and excellent performance, with advantages such as low cost, easy preparation and high environmental stability. Selecting TMOs with different band gaps, work functions and conductivity to construct heterojunctions with TMDs not only improves the latter's physical and chemical properties, but also further broadens its functionality, with broader application scenarios in photonics and electronics and other fields.

[0004] Mechanical exfoliation is a traditional method for preparing heterojunctions. Although it can produce high-quality heterojunctions, it can only produce thin layers of materials with small size and random shapes. In contrast, the CVD method can achieve the preparation of large-area, high-quality, shape-controlled, and layer-controlled two-dimensional material heterojunctions. Summary of the invention

[0005] The purpose of the present invention is to provide a simple, efficient and large-scale CVD method for preparing TMDs / TMOs heterojunctions. The TMDs / TMOs heterojunction is formed by partially sulfiding TMOs by adding chalcogen monomers.

[0006] The method for in-situ preparation of TMDs / TMOs heterojunction based on sulfurized TMOs comprises:

[0007] 1) Cleaning a substrate, wherein the substrate is a metal substrate or a non-metal substrate;

[0008] 2) Place 65-95 mg of chalcogen, 90-100 mg of TMOs, and substrate into a quartz tube in sequence. Place TMOs in a quartz boat, 18-22 cm upstream of TMOs, and 3-5 cm downstream of substrate.

[0009] 3) Place the quartz tube in the muffle furnace, first pass Ar gas with a flow rate of 100 sccm, exhaust the air in the tube, and heat the muffle furnace under the protection of Ar atmosphere. After the central temperature zone rises to 895-905℃, move the muffle furnace until the substrate is located in the central temperature zone;

[0010] 4) Move the muffle furnace until the substrate leaves the central temperature zone, quickly cool it to room temperature, and turn off the Ar gas;

[0011] The chalcogen element is S, Se or Te; the TMOs include MoO3, WO3, MoO2, WO2; The temperature of the chalcogenide and the substrate is 350 °C

[0012] The furnace temperature is raised from room temperature to 750°C within 30 minutes, and then raised to the growth temperature of 900°C within 15 minutes.

[0013] Step 1) The substrate is cleaned as follows: the substrate is first cleaned with deionized water, acetone, isopropanol, and ultrasonically cleaned in ethanol for 30 min; the cleaned substrate is placed in a muffle furnace and 50 sccm argon and 50 sccm hydrogen are introduced, and annealed at 1050° C. for 12 h.

[0014] The substrate is gold foil or silicon wafer; the TMOs is TMOs; and the chalcogen element is Se powder.

[0015] Adjusting the sulfur source content can adjust the layer thickness of the heterojunction to obtain single-layer TMDs / TMOs and multi-layer TMDs / TMOs;

[0016] The sulfur element is 65-70 mg or 90-95 mg.

[0017] The advantages and beneficial effects of the present invention are:

[0018] 1) Efficient one-step preparation process:

[0019] The present invention adopts a CVD method to prepare a TMDs / TMOs heterojunction in one step, simplifies the preparation process, and improves production efficiency. Compared with the traditional multi-step preparation method and stripping method, such as preparing TMOs first and then sulfurizing, the present invention reduces the preparation steps and intermediate links, and reduces the pollution generated during the preparation process. At the same time, by optimizing the growth conditions, a TMDs / TMOs heterojunction with excellent optoelectronic performance and stability can be prepared.

[0020] 2) Precise control of the vulcanization process:

[0021] By precisely controlling the amount of sulfur source added and growth conditions (such as temperature, gas flow rate, etc.), the present invention achieves precise control of the partial sulfurization process of TMOs. This helps to form a high-quality TMDs / TMOs heterojunction and ensures that the interface of the heterojunction is clear and the crystallinity is high.

[0022] 3) Wide range of material applicability:

[0023] The present invention is not only applicable to a specific combination of TMOs and TMDs materials, but also has certain material applicability. By adjusting the types of sulfur sources and TMOs, different types of TMDs / TMOs heterojunctions can be prepared to meet the needs of different fields.

[0024] The present invention forms a TMDs / TMOs heterojunction by partially sulfurizing TMOs by adding a chalcogenide element. The prepared heterojunction has high crystalline quality and large size. The thickness of the heterojunction can be precisely controlled by changing the amount of the chalcogenide element. The heterojunction can also be grown on different types of substrates.

[0025] In summary, the present invention adopts the CVD method to in-situ prepare TMDs / TMOs heterojunction, which not only solves the problems of complex operation and small sample size in the traditional preparation method, but also provides a new idea and method for the preparation of two-dimensional material heterojunction. This heterojunction has broad application prospects in the fields of electronic devices, optoelectronic devices, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Experimental device for preparing TMDs / TMOs heterojunction; a is a schematic diagram before / after the reaction, b is a schematic diagram during the reaction: 1 gas inlet; 2 sulfide element; 3 growth source; 4 growth substrate; 5 central temperature zone; 6 gas outlet; c is a schematic diagram of the muffle furnace heating;

[0027] Figure 2 Optical image of heterojunction prepared by CVD method; a is a scanning electron microscope image of a single-layer MoSe2 / MoO2 heterojunction; b is an atomic force image of a single-layer MoSe2 / MoO2 heterojunction; c is a Raman spectrum of a single-layer MoSe2 / MoO2 heterojunction;

[0028] Figure 3 Optical image of multilayer heterojunction prepared by CVD method; a is a scanning electron microscope image of multilayer MoSe2 / MoO2 heterojunction; b is an atomic force image of multilayer MoSe2 / MoO2 heterojunction;

[0029] Figure 4 Optical image of heterojunction grown on non-metallic substrate; a is the microscope optical image of MoSe2 / MoO2 heterojunction; b is the Raman spectrum of MoSe2 / MoO2 heterojunction. DETAILED DESCRIPTION

[0030] Example 1 A method for in-situ preparation of a single-layer TMDs / TMOs heterojunction by sulfiding TMOs

[0031] A method for preparing a single-layer TMDs / TMOs in-situ heterojunction, using a CVD method to prepare the heterojunction in one step, using a chalcogenide element to partially sulfide TMOs to form a TMDs layer. Taking the preparation of a single-layer molybdenum selenide (MoSe2) / molybdenum dioxide (MoO2) heterojunction as an example, molybdenum trioxide (MoO3) powder is a growth source, selenium (Se) powder is a sulfide element, and gold foil is a growth substrate. The specific steps are as follows:

[0032] Before preparation, in order to make the growth substrate gold foil (10 mm×10 mm×100 μm, purity 99.99 wt%) clean and flat, the gold foil was first ultrasonically cleaned in deionized water, acetone, isopropanol, and ethanol for 30 min. The cleaned gold foil was placed in a muffle furnace with a flow rate of 50 sccm argon (Ar) and 50 sccm hydrogen (H2) and annealed at 1050 ℃ for 12 h. Figure 1 As shown in a, a muffle furnace is used for growth. The growth source and substrate are placed in a quartz tube, and a gas inlet 1 and a gas outlet 6 are provided at both ends of the tube; Se powder is located at 2; MoO3 powder is located at 3; gold foil is placed at position 4; before and after the reaction, the central temperature zone of the horizontal muffle furnace is located at position 5. Then 100 mg of MoO3 powder (growth source) (purity of 99.99%) is placed in a quartz boat, the treated gold foil is placed 3 cm behind MoO3, and 70 mg of Se powder (purity of 99.999%) is placed about 20 cm upstream (350 °C).

[0033] After the preparation work is completed, pass Ar with a flow rate of 100 sccm for 5 minutes to exhaust the air in the tube. In the Ar atmosphere, start the muffle furnace and set the following Figure 1c, first from room temperature to 750 °C within 30 min, and then to the growth temperature of 900 °C within 15 min. After reaching the growth temperature, the muffle furnace is quickly pushed so that the central temperature zone is located at the growth substrate, position 4. After the MoO3 and Se powder are evaporated by heat, they will diffuse to the surface of the growth substrate gold foil at position 4 with the carrier gas (Ar), and a reduction reaction will occur to form MoO2. In the further selenium-rich atmosphere, MoO2 is partially selenized to form a MoSe2 / MoO2 heterojunction. The total growth time is 20 min. After the reaction is completed, the muffle furnace is pushed back to the right to position 5, so that the growth substrate gold foil is quickly cooled from 900 °C to room temperature. When it cools to room temperature, the Ar is turned off, the growth substrate is taken out, and the MoSe2 / MoO2 heterojunction is obtained on its surface.

[0034] Compared with the existing vapor deposition process, the size of the heterojunction grown by the method of the present invention is much larger than that of the existing process. Figure 2 It was observed from a scanning electron microscope in a that the size of the rectangular MoO2 in the heterojunction is about 10~20 μm, and the size of the triangular MoSe2 grown epitaxially on it is about 30~50 μm. Figure 2 b is an atomic force microscope image of a MoSe2 / MoO2 heterojunction, where the rectangular nanosheet is about 28 nm thick and is MoO2; on it is distributed MoSe2 with a thickness of about 0.9 nm. If the thickness of TMDs is within 1 nm, it can be judged as a single layer. Figure 2 c is the Raman spectrum of the heterojunction. Several main Raman modes of MoO2 (125, 202, 228, 343, 360, 466, 495, 569, 585 and 741 cm) can be observed simultaneously. −1 ) and A of MoSe2 1g (238 cm -1 ) mode, E 1 2g (285 cm -1 ) mode, proving that a high-crystalline quality MoSe2 / MoO2 heterostructure was obtained. -1 There is no Raman characteristic peak, which confirms the single-layer structure of MoSe2.

[0035] Example 2 A method for in-situ preparation of multilayer TMDs / TMOs heterojunction by sulfurizing TMOs

[0036] A method for preparing a multilayer TMDs / TMOs heterojunction, using a CVD method to prepare a heterojunction in one step, taking a MoSe2 / MoO2 heterojunction as an example, by changing the amount of Se powder, adjusting the layer thickness of the heterojunction, a multilayer MoSe2 / MoO2 heterojunction is obtained. MoO3 powder and are used as growth sources, Se powder is a sulfide element, and gold foil is used as a growth substrate. The specific steps are as follows:

[0037] The growth source and the gold foil substrate were placed in a 1.2m long quartz tube, with a gas inlet 1 and a gas outlet 6 at both ends of the tube; Se powder was located at position 2; MoO3 was located at position 3; the gold foil was placed at position 4; before and after the reaction, the central temperature zone of the horizontal muffle furnace was located at position 5. 100 mg of MoO3 powder (purity of 99.99%) was placed in a quartz boat, and the treated gold foil was placed in the same quartz boat 3 cm behind MoO3, where MoO3 was located at 900 ℃ in the central temperature zone of the muffle furnace. The amount of Se powder (purity of 99.999%) was changed to 90 mg, and it was located about 20 cm upstream of MoO3 (350 ℃).

[0038] After the preparation work is completed, Ar is introduced for 5 min to exhaust the air in the tube. Under the protection of Ar atmosphere, the muffle furnace is started and the temperature is increased in two stages, first from room temperature to 750 ℃ ​​within 30 min, and then from 750 ℃ ​​to the growth temperature of 900 ℃ within 15 min. After reaching the growth temperature, the muffle furnace is quickly pushed so that the central temperature zone is located at the growth substrate, position 4. After the MoO3 and Se powder are evaporated by heat, they will diffuse to the surface of the growth substrate gold foil at position 4 with the carrier gas (Ar), and a reduction reaction will occur to form MoO2. In the selenium-rich atmosphere, MoO2 is partially selenized to form a MoSe2 / MoO2 heterojunction. The growth time of the reaction is 20 minutes. After the reaction is completed, the muffle furnace is pushed back to the right to position 5, so that the growth substrate gold foil is quickly cooled from 900 ℃ to room temperature. When it cools to room temperature, Ar is turned off, the growth substrate is taken out, and a multilayer MoSe2 / MoO2 heterojunction is obtained on its surface.

[0039] This embodiment is compared with the embodiment 1, the amount of sulfurized elemental Se powder is changed, and the other experimental steps are exactly the same, so as to achieve precise control of the number of heterojunction layers. Figure 3 a, Multilayer MoSe2 / MoO2 heterojunction was observed using a scanning electron microscope. As the Se content increased, the triangular MoSe2 single crystal regions connected to form a MoSe2 thin film, and the sample appeared uniform gray-black, indicating that the number of sample layers was very uniform, forming a MoSe2 / MoO2 heterojunction. Figure 3 b is an atomic force microscope image of the MoSe2 / MoO2 heterojunction, in which the thickness of the rectangular MoO2 is about 80 nm and the thickness of the MoSe2 thereon is about 2.1 nm, forming a multilayer MoSe2 / MoO2 heterojunction different from that in Example 1.

[0040] Example 3 A method for in-situ preparation of TMDs / TMOs heterojunction on a non-metallic substrate by sulfiding TMOs

[0041] A method for preparing a TMDs / TMOs heterojunction on a non-metallic substrate, taking the preparation of MoSe2 / MoO2 as an example, a heterojunction is prepared in one step by a CVD method on a non-metallic substrate such as silicon or sapphire. This example proves that the method for preparing a MoSe2 / MoO2 heterojunction growth substrate is universal, and can be grown not only on gold foil, but also on a non-metallic substrate. The specific steps are as follows:

[0042] The growth source and the gold foil substrate were placed in a 1.2m long quartz tube, with a gas inlet 1 and a gas outlet 6 at both ends of the tube; Se powder was located at 2; MoO3 was located at 3; the gold foil was placed at position 4; before and after the reaction, the central temperature zone of the horizontal muffle furnace was located at position 5. Then 70 mg of Se powder (purity of 99.999%) was placed about 20 cm (350 ℃) upstream, and 100 mg of MoO3 powder (purity of 99.99%) was placed in a quartz boat. A clean non-metallic substrate silicon wafer (10 mm×10 mm×400 μm, single-sided polished) was placed 3 cm behind the MoO3 powder.

[0043] After the preparation work is completed, 100 sccm of Ar is introduced for 5 minutes to exhaust the air in the tube. Under the protection of Ar atmosphere, the muffle furnace is started and the temperature is increased at a two-stage rate, from room temperature to 750 °C in 30 minutes, and then from 750 °C to the growth temperature of 900 °C in 15 minutes. After reaching the growth temperature, the muffle furnace is quickly pushed so that the central temperature zone is located at the growth substrate, position 4. After the MoO3 and Se powder are evaporated by heat, they will diffuse to the surface of the growth substrate silicon wafer at position 4 with the carrier gas (Ar), and a reduction reaction will occur to form MoO2. In the selenium-rich atmosphere, MoO2 is partially selenized to form a MoSe2 / MoO2 heterojunction. The growth time of the reaction is 20 minutes. After the reaction is completed, the muffle furnace is pushed back to the right to position 5, so that the growth substrate silicon wafer is quickly cooled from 900 °C to room temperature. When it cools to room temperature, the Ar is turned off, the growth substrate is taken out, and the MoSe2 / MoO2 heterojunction is obtained on its surface.

[0044] like Figure 4 a, MoSe2 / MoO2 heterojunction observed under an optical microscope. A single layer of MoSe2 is epitaxially grown on a square MoO2 (about 5~20 μm). Unlike MoSe2 on a gold foil substrate, the area of ​​MoSe2 on the silicon wafer is smaller and not triangular. Figure 4 b is the Raman spectrum of the MoSe2 / MoO2 heterojunction, where several main Raman modes of MoO2 (125, 202, 228, 343, 360, 466, 495, 569, 585, and 741 cm) can be observed simultaneously. −1 ) and A of MoSe2 1g (238 cm -1) mode, E 1 2g (285 cm -1 ) mode, proving that a MoSe2 / MoO2 heterostructure was obtained on a non-metallic substrate silicon wafer. -1 There is no Raman characteristic peak at the position, which confirms the monolayer structure of the grown MoSe2. This example proves that this method can grow MoSe2 / MoO2 heterojunctions on gold foil substrates and non-metallic substrates, and has a certain universality.

Claims

1. A method for in-situ preparation of TMDs / TMOs heterojunction based on sulfurized TMOs, comprising: 1) Cleaning a substrate, wherein the substrate is a metal substrate or a non-metal substrate; 2) Place 65-95 mg of chalcogen, 90-100 mg of TMOs, and substrate into a quartz tube in sequence. Place TMOs in a quartz boat, 18-22 cm upstream of TMOs, and 3-5 cm downstream of substrate. 3) Place the quartz tube in the muffle furnace, first pass Ar gas with a flow rate of 100 sccm, exhaust the air in the tube, and heat the muffle furnace under the protection of Ar atmosphere. After the central temperature zone rises to 895-905℃, move the muffle furnace until the substrate is located in the central temperature zone; 4) Move the muffle furnace until the substrate leaves the central temperature zone, quickly cool it to room temperature, and turn off the Ar gas.

2. The method for in-situ preparation of TMDs / TMOs heterojunction based on sulfurized TMOs according to claim 1, characterized in that: The chalcogen element is S, Se or Te; the TMOs include MoO3, WO3, MoO2, and WO2.

3. The method for in-situ preparation of TMDs / TMOs heterojunction based on sulfurized TMOs according to claim 2, characterized in that: The furnace temperature is raised from room temperature to 750°C within 30 minutes, and then raised to the growth temperature of 900°C within 15 minutes.

4. The method for in-situ preparation of TMDs / TMOs heterojunction based on sulfurized TMOs according to claim 3, characterized in that: Step 1) The substrate is cleaned as follows: the substrate is first cleaned with deionized water, acetone, isopropanol, and ultrasonically cleaned in ethanol for 30 min; the cleaned substrate is placed in a muffle furnace with a flow rate of 50 sccm argon and 50 sccm hydrogen, and annealed at 1050°C for 12 h.

5. The method for in-situ preparation of TMDs / TMOs heterojunction based on sulfurized TMOs according to claim 4, characterized in that: The substrate is gold foil or silicon wafer, the TMOs is TMOs, and the chalcogenide element is Se powder.

6. The method for in-situ preparation of TMDs / TMOs heterojunction based on sulfurized TMOs according to claim 1, 2, 3, 4 or 5, characterized in that: The sulfur element is 65-70 mg or 90-95 mg.

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